1. Technical Field
Exemplary embodiments of the present disclosure generally relate to a cleaning blade, an electrophotographic image forming apparatus employing the cleaning blade, and a process cartridge detachably attached with respect to the image forming apparatus.
2. Related Art
In conventional electrophotographic image forming apparatuses, after a toner image is transferred to an intermediate transfer body or a transfer sheet, an unnecessary transfer residue toner adhering to a surface of an image carrier such as a photoreceptor serving as a cleaning target member is removed by a cleaning device serving as a cleaning mechanism. A configuration of the cleaning device is typically simple and from a point of good cleaning performance, employing a strip shaped cleaning blade is well known. The cleaning blade is configured of a blade member formed of an elastic member such as a polyurethane rubber. A base end of the blade member is supported by a supporting member and a leading-edge ridge line portion contacts the surface of the image carrier. The transfer residue toner on the image carrier is removed by stopping and scraping off with the blade member.
In conventional cleaning blades, the blade member having a single layer configuration of a low hardness polyurethane rubber is widely employed.
In JP-2007-086202-A and JP-2011-197309-A, a cleaning blade employing a blade member having a laminated structure including an edge layer having a leading-edge ridge line portion that contacts the image carrier formed of a comparatively high hardness rubber material and a backup layer formed of a rubber material having a hardness lower than the edge layer is disclosed.
In recent years, in addition to high reliability and high operational life of an image forming apparatus, energy saving in the image forming apparatus is becoming more and more important due to heightened environmental awareness. Energy saving in a fixing process of the image forming apparatus that consumes the most energy in the image forming apparatus is an important challenge for energy saving, and development of energy saving technology of the fixing device and development of a low temperature fixing toner are being actively conducted. In the low temperature fixing toner, a toner needs to gum/soften at a further low temperature. In accordance with making the toner gum/soften at the further low temperature, a glass transition temperature declines. For example, the toner having the glass transition temperature (Tg) in a range from 40° C. to 60° C. has been developed.
In continuous action of image formation with the image forming apparatus, an internal temperature of the image forming apparatus rises. In a temperature range from 10° C. to 35° C. conceivable in a typical office environment, the internal temperature of the image forming apparatus may rise to around a glass transition temperature or more of a low temperature fixing toner. For example, in a middle speed apparatus, an internal temperature of the middle speed apparatus may rise to around a glass transition temperature of 60° C. of a low temperature fixing toner. In a high speed apparatus, there is a case in which an internal temperature of the high speed apparatus rises even higher than around a glass transition temperature of a low temperature fixing toner. In addition, in a cleaning blade system, a friction heat is generated by a sliding friction force between the image carrier and the blade member at a contact portion, and a temperature of the leading-edge ridge line portion of the blade member rises even higher than the internal temperature.
In the cleaning blade system, the leading-edge ridge line portion of the blade member contacts the surface of the image carrier that moves, and the leading-edge ridge line portion stops and removes the transfer residue toner. However, the leading-edge ridge line portion of the blade member deforms and is drawn towards the moving direction of the image carrier due to the sliding friction force between the image carrier and the blade member. Accordingly, a portion of the stopped transfer residue toner slips through the leading-edge ridge line portion little by little. The transfer residue toner is pressed against the image carrier when the transfer residue toner slips through the leading-edge ridge line portion little by little.
In a case of employing the low temperature fixing toner, the low temperature fixing toner adheres to the image carrier by easily gumming/softening due to the temperature rise of the leading-edge ridge line portion and a pressing force when the low temperature fixing toner slips through the deformed leading-edge ridge line portion little by little. The transfer residue toner adhering to the surface of the image carrier becomes a film over time and filming is generated on the surface of the image carrier. When filming is generated, problems such as image density unevenness, cleaning failure, and charging failure are generated.
JP-2007-086202-A and JP-2011-197309-A describe suppression of deformation of the leading-edge ridge line portion of the edge layer in the blade member formed of the comparatively high hardness rubber material, and slipping through of the transfer residue toner through the leading-edge ridge line portion becoming difficult. Accordingly, the blade member of JP-2007-086202-A and JP-2011-197309-A are thought to be advantageous in suppressing the generation of filming by the low temperature fixing toner. However, conditions of the comparatively high hardness rubber material are not considered for favorably suppressing the generation of filming by the low temperature fixing toner.
In JP-2007-086202-A, a hardness of the edge layer including a vicinity of the leading-edge ridge line portion is determined as a rubber hardness of 75 to 90 measured with a JIS-A measurement method commonly employed to represent hardness of a rubber material. However, in a blade member configured of a comparatively thin edge layer and the backup layer, when a rubber hardness of the comparatively thin edge layer is measured from a surface perpendicular to the laminated direction of the backup layer with the JIS-A measurement method, a measured value of the rubber hardness of the comparatively thin edge layer includes influence of the backup layer. Accordingly, employing a rubber hardness measured with the JIS-A measurement method as an index of a hardness of the leading-edge ridge line portion of the blade member for suppressing filming by the low temperature fixing toner may lead to, depending on position of hardness measurement, not obtaining sufficient suppressing effect by the leading-edge ridge line portion of the blade member.